Method of forming contacts for a back-contact solar cell

Abstract

Methods of forming contacts for back-contact solar cells are described. In one embodiment, a method includes forming a thin dielectric layer on a substrate, forming a polysilicon layer on the thin dielectric layer, forming and patterning a solid-state p-type dopant source on the polysilicon layer, forming an n-type dopant source layer over exposed regions of the polysilicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped polysilicon regions among a plurality of p-type doped polysilicon regions.

What is claimed is: 
     
       1. A method of forming contacts for a back-contact solar cell, the method comprising:
 forming a thin dielectric layer on a substrate; 
 forming a polysilicon layer on the thin dielectric layer; 
 forming and patterning a solid-state p-type dopant source on the polysilicon layer, the patterning exposing regions of the polysilicon layer between a plurality of regions of the solid-state p-type dopant source; 
 forming an n-type dopant source layer over the exposed regions of the polysilicon layer and the plurality of regions of the solid-state p-type dopant source, the forming comprising at least partially driving dopants from the n-type dopant source layer into the exposed regions of the polysilicon layer to form a plurality of n-type dopant-containing polysilicon regions between the plurality of regions of the solid-state p-type dopant source; and, subsequently, 
 heating the substrate to provide a plurality of n-type doped polysilicon regions among a plurality of p-type doped polysilicon regions and, prior to the heating, removing the plurality of regions of the solid-state p-type dopant source. 
 
     
     
       2. The method of  claim 1 , further comprising:
 subsequent to forming an n-type dopant source layer and prior to heating the substrate, forming trenches between the plurality of n-type dopant-containing polysilicon regions and the plurality of regions of the solid-state p-type dopant source, the trenches formed in the polysilicon layer, in the thin dielectric layer, and partially in the substrate. 
 
     
     
       3. The method of  claim 2 , further comprising:
 subsequent to forming the trenches and prior to heating the substrate, texturizing portions of the substrate exposed by the trenches. 
 
     
     
       4. The method of  claim 3 , wherein forming the trenches and the texturizing is performed without a cure operation between the forming the trenches and the texturizing. 
     
     
       5. The method of  claim 1 , wherein forming the n-type dopant source layer further comprises at least partially driving dopants from the plurality of regions of the solid-state p-type dopant source into the polysilicon layer. 
     
     
       6. The method of  claim 5 , wherein heating the substrate comprises activating the dopants in the plurality of n-type dopant-containing polysilicon regions, furthering the driving of dopants originating from the plurality of regions of the solid-state p-type dopant source into the polysilicon layer, and activating the dopants of the plurality of regions of the solid-state p-type dopant source in the polysilicon layer. 
     
     
       7. The method of  claim 1 , wherein forming and patterning the solid-state p-type dopant source comprises forming and patterning a layer of boron silicate glass (BSG). 
     
     
       8. The method of  claim 1 , wherein forming the n-type dopant source layer comprises forming a layer of P 2 O 5 . 
     
     
       9. The method of  claim 1 , further comprising:
 forming, by laser ablation, a plurality of contact openings to the plurality of n-type doped polysilicon regions and the plurality of p-type doped polysilicon regions. 
 
     
     
       10. A solar cell fabricated according to the method of  claim 1 . 
     
     
       11. A method of forming contacts for a back-contact solar cell, the method comprising:
 forming a thin dielectric layer on a substrate; 
 forming a polysilicon layer on the thin dielectric layer; 
 forming and patterning a solid-state p-type dopant source on the polysilicon layer, the patterning exposing regions of the polysilicon layer between a plurality of regions of the solid-state p-type dopant source; 
 loading the substrate in a reaction chamber and, without removing the substrate from the reaction chamber, both forming an n-type dopant source layer over the exposed regions of the polysilicon layer and the plurality of regions of the solid-state p-type dopant source and at least partially driving dopants from the n-type dopant source layer into the exposed regions of the polysilicon layer to form a plurality of n-type dopant-containing polysilicon regions between the plurality of regions of the solid-state p-type dopant source; 
 removing the substrate from the reaction chamber; and, subsequently, 
 heating the substrate to provide a plurality of n-type doped polysilicon regions among a plurality of p-type doped polysilicon regions. 
 
     
     
       12. The method of  claim 11 , further comprising:
 subsequent to forming an n-type dopant source layer and prior to heating the substrate, forming trenches between the plurality of n-type dopant-containing polysilicon regions and the plurality of regions of the solid-state p-type dopant source, the trenches formed in the polysilicon layer, in the thin dielectric layer, and partially in the substrate. 
 
     
     
       13. The method of  claim 12 , further comprising:
 subsequent to forming the trenches and prior to heating the substrate, texturizing portions of the substrate exposed by the trenches. 
 
     
     
       14. The method of  claim 13 , wherein forming the trenches and the texturizing is performed without a cure operation between the forming the trenches and the texturizing. 
     
     
       15. The method of  claim 11 , wherein forming the n-type dopant source layer further comprises at least partially driving dopants from the plurality of regions of the solid-state p-type dopant source into the polysilicon layer. 
     
     
       16. The method of  claim 15 , wherein heating the substrate comprises activating the dopants in the plurality of n-type dopant-containing polysilicon regions, furthering the driving of dopants originating from the plurality of regions of the solid-state p-type dopant source into the polysilicon layer, and activating the dopants of the plurality of regions of the solid-state p-type dopant source in the polysilicon layer. 
     
     
       17. The method of  claim 11 , further comprising:
 while the substrate is loaded in the reaction chamber, at least partially driving dopants from the solid-state p-type dopant source into the polysilicon layer. 
 
     
     
       18. A solar cell fabricated according to the method of  claim 11 .